This disclosure generally relates to devices and methods for providing support to wire harnesses in a vibration environment. In particular, this disclosure relates to devices and methods for providing support to a wire harness that is coupled to a backshell assembly comprising a backshell, strain relief arms, and a cable clamp.
A wire harness is an assembly of cables or wires which transmit signals or electrical power. The cables are bound together by straps, cable ties, cable lacing, sleeves, electrical tape, a conduit, a weave of extruded string, or a combination thereof. By binding many wires or cables into a wire harness, the wires or cables can be better secured against the adverse effects of vibration, abrasion, and moisture.
In cable assemblies, wires and cables of a wire harness act as antennas to pick up and/or radiate noise from and/or to other cables. One solution to this cross-talk problem is to apply conductive braided shielding around cable conductors, and attach the shielding to an electrical ground, thereby reducing or eliminating any effects of any electrical and magnetic fields resulting from such radiation.
It is known to terminate a wire harness at a cable termination and grounding assembly. A cable termination and grounding assembly can be used as an electromagnetic interference (EMI)/high-intensity radiated field (HIRF) grounding device providing high surface transfer impedance shielding, noise immunity and susceptibility at all frequency ranges and as a strain relief device providing mechanical support or both in an assembly of electrical shielded cable. Each cable typically includes numerous wires that are connected to a connector and at least one electrically conductive shield or braid that offers protection from electromagnetic emissions, electromagnetic susceptibility, and electromagnetic crosstalk between wires of one or more cables. The shield must be properly terminated at the connector. In many cable termination and grounding assemblies, the signal wire connections and the shield terminations are covered by a backshell, which is a cover that is coupled to the connector to provide protection from physical contact and prevent electromagnetic interference (EMI) from outside sources and electromagnetic emissions from the cable wires. An electrically conductive cable overbraid shield is terminated to the backshell to prevent radiation from entering at the backshell/shield interface.
Many known backshell assemblies provide a transition from a plurality of electrical conductors to an electrical connector. In particular, some backshell assemblies comprise a mechanical cable clamp that provides a radial clamping force relative to a wire bundle to prevent axial forces from damaging the termination of the wires at the electrical connector. This cable clamp may comprise a pair of saddle bars coupled to the backshell by means of pivotable strain relief arms and joined to each by conventional fasteners.
In addition, it is known to provide a split shield termination ring which is placed around a portion of a shielded cable at a short distance from the aforementioned cable clamp of the backshell assembly. Typically the overall braided shielding surrounding the cable is folded back over the shield termination ring. Later the overall braided shielding from the backshell assembly is pulled over the folded-back cable braided shielding.
In some circumstances, a connector-backshell-shield termination ring installation of the above-described type may exhibit shield braid and wire insulation fatigue failures in service due to the existing vibration environment. The installation may allow the wire harness and the shield termination ring to move excessively, causing shield braid and wire insulation fatigue failures between the backshell and the shield termination ring. This is a result of a lack of strain relief in the region to the rear of the backshell cable clamp.
One proposed solution is to wrap the harness with tape from the shield termination ring to a point near the connector. Another proposed solution is to install rubber sleeving. Both of these solutions require wrapping the harness with tape, which is time consuming and may not adequately prevent excess flexure of the harness in service.
An installation is needed that will reduce or prevent movement of the wire harness and the shield termination ring when a wire harness termination assembly is in service.